let arg=process.argv[2];

function calculate(arg){
    //eval(js语句)，执行JS得到结果
    let result=eval(arg)
    if(!isNaN(Number(result))){
        console.log(arg+"="+result);
    }else{
        console.log("result is not number")
    }
}

switch(arg){
    case "-h":
        consolelog("help information!...")
        break;
    default:
        calculate(arg);
}